Note 4 - Inventories (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Inventory Write-down	$ 200	$ 0	$ 288	$ 0
Systems [Member]
Inventory Write-down	$ 200	$ 0	$ 300	$ 0